José Mourinho says Chelsea had "learned to live without pain" in recent seasons after bad results and he believes the squad's mentality must harden if they are to challenge for the Premier League title.

The manager, who returned in June for his second spell in charge, noted how the club had won the Champions League in 2012 and enjoyed other eye-catching results. But he suggested their league finishes in the past two seasons highlighted not only a lack of consistency but an acceptance of being second best at times. Chelsea were 14 points off the pace last season; 25 behind in 2011-12.

Mourinho has been pleased at how his developing team have responded to their back-to-back defeats at the hands of Everton and Basel in the middle of September. They were particularly resilient and expressive in the second half at Tottenham Hotspur last Saturday, in the 1-1 draw, before they won 4-0 at Steaua Bucharest in a high-pressure Champions League tie on Tuesday.

Mourinho felt the confidence of his players in training; they could "breathe in a different way," according to him. But he does not want to see them relax at Norwich City on Sunday and he pulled no punches in his message to them.

"We're not strong enough now to have that run of victory, victory, victory," Mourinho said. "We will, for sure, but not now. It comes from work, work, work … change their mentality by working. Make them feel and accept the responsibility of playing for a big club with big ambition, where you can't go win-lose-win-lose. This mental stability is hard to get.

"You can see two seasons ago, [the club] won the Champions League but finished sixth, 25 points behind. Last year [they] finished third but in December/January, were 15 points behind the first. This kind of team personality ... you can't win leagues like that. For a club like us, [it is] not good to be so far behind. Some fantastic performances but better to win seven [games] 1-0 than one 7-0 and lose points in others. This is the mentality we have to build and it's much more difficult.

"I'm not saying the club had [a poor mentality]. But they learned how to live without pain in a situation where, with another mentality, it would be painful. The day I lose and go home with a smile ... goodbye. Finish. It's something you have naturally or you get it. You have to get it."

Mourinho spoke of his three years as the Real Madrid manager, which were marked by struggles in La Liga against Barcelona, where the margins for error were virtually nonexistent. It further toughened his mentality and he wants to instil something similar at Chelsea.

"When I say it's more difficult to win in Spain, it's not because the teams are better," Mourinho said. "No way. But if Real Madrid don't win a match, I'm in big trouble because Barcelona don't lose. It's not easy in Spain because you have to win every game and that pressure is very difficult.

"We need to educate our people to play under this pressure. Don't accept defeat easily or think one point is good enough. It's not easy to build that into a team. My old Chelsea team [in 2004-07] had this mentality. We have to play every game of every competition to win."

Mourinho said his second spell at is more challenging than the first because of what he has to instil in younger players. "It's because of profile, stability and maturity," he said. "I had a team in the best moment of their careers, where they just needed a click to make them believe. Now it's building a team. It takes more than one click to recover 20 points. Individually, everyone has to look for something extra."